The present invention is with respect to a process and an apparatus for the production of single-base and multi-base propellant in the form of rods using a double shaft screw extruder with an intake zone for the starting components, of which at least one is moistened with alcohol, and next thereto a mixing and kneading zone with means for the addition of solvent for plastifying the material and an outlet zone after the said screws with a forming head for one or more rods, the said intake zone being kept at a raised temperature.
For the production of single-base propellants (nitrocellulose), double-base propellants (nitrocellulose+nitroglycerin or other liquid explosive), and furthermore triple-base propellants (nitrocellulose+nitroglycerin+nitroguanidine), thermoplastic molding processes or more specially molding processes using volatile solvent are used. The solvent or gelling agents are as a rule ketones, alcohols, ethers or mixtures thereof. The solvent process outdoes the thermoplastic molding or forming method on safety grounds inasfar as the addition of the solvents makes for a relatively low working temperature, and for example nitrocellulose that has been turned into a doughy mass in this way may be extruded from a screw extruder as one or more rods (see German Auslegeschrift specification No. 2,825,567 and the German Offenlegungsschrift specification No. 3,044,577), in which respect, dependent on the field of use one or more needle cores are used in the die so that the rods are formed with one or more holes therein.
Because of internal friction high temperatures are produced in such molding processes, so that in the past attempts have been at keeping the apparatus cool by the addition of excess solvent or by cooling the extruder in the kneading or mixing zone (see said German Auslegeschrift specification No. 2,825,567) so as to keep the temperature within safe limits. In the first case of the addition of excess solvent the extrude has to undergo a drying process for clearing the rest of the solvent therefrom before it may undergo further processing. In this case as well the material does not in all cases keep its shape and the holes therein may be changed in form in an undesired way. In both the two said cases the quality of the final product is not good enough, more specially in respect of density and homogeneity. It is however these very factors, namely dimensional stability, density and homogeneity, that are likely to have a very marked effect on the ballistic properties. Although with the controlled addition of solvent (as in the said German specification No. 3,044,577) very much better effects are possible, the throughput rate is not as desired.